Presentation on theme: "Three Domains of Life Protists"— Presentation transcript:
1 Three Domains of Life Protists Archea have classified Kingdoms; Bacteria do not (yet)On the contrary, Eukaryota is composed of well-defined Kingdoms including Plants, Fungus and Animals; the exception is Protists which we’ll discover are not monophyletic and include groups that are similar in design, but not in evolutionary processes
3 Changes in Classification The ‘old school’ method of classification included 5 Kingdoms (what I learned in school)MoneraProtistaFungiPlantaeAnimaliaToday, advances in molecular technology expanded our understanding (and interpretation) of systematics
4 Modern Systematics Three Domain classification of life Numerous, virtually countless KingdomsBacteria and Archaea are now 2 distinct Domains (once included together in Kingdom Monera)Protista, Fungi, Plantae, and Animalia remain classified as distinct Kingdoms, although classification of the kingdom Protista has been met with complications
5 Prokaryotes Includes the kingdoms Archaea & Bacteria Oldest, structurally-simplest, and most abundant forms of lifePhotosynthesis Bacterial and Eukaryotic DiversityImportant decomposers and symbiontsTrue bacteria; Existed on Earth for 1 billion years before the Eukaryotes appeared
6 Prokaryotes Unicellular Typically 1μm or less (1000 μm = 1mm; 1000mm = 1 meter)No membrane-bound nucleus; instead a single circular chromosome made of DNAAsexual reproduction by binary fissionPhotosynthetic bacteria utilize oxygen or chemical compounds, such as sulfurAlthough they can transfer genetic material via their plasmids (horizontal gene transfer), however not considered reproduction
7 Prokaryotic Cell Structure Three basic forms:Bacillus – rod-shapedCoccus - sphercal or ovoid-shapedSpirillum – spiral or helical
8 Prokaryotic Cell Structure Prokaryotes have a tough cell wall and other external structuresCell wall consists of peptidoglycan; a rigid network of polysaccharide strands cross-linked by peptide side chains; unique to BacteriaMaintains the shape of the cell and protects it from swelling and rupturing
9 Prokaryotes can have 1 or more flagella (much less complex than in Eukaryotes) Some Prokaryotes possess pilli, which helpsfasten cell to host membrane
10 Domain ArchaeaOnce considered a subdivision of the Kingdom Monera, now its own domainLike all prokaryotes, Archaea are single-celled microorganisms that lack a nucleus and membrane-bound organellesBest known for the “extremophiles” – Archaea which thrive in extremely harsh environments
11 Archea - Extremophiles Thermophiles – thrive at 60-80°C (>176°F!)Acidophiles – thrive at pH at or below pH 3Xerophiles – grow in extremely dry conditionsHalophiles – require extremely high concentrations of salt
12 Archaea - Extremophiles Evidence for evolution of life on Earth?Many of the harsh conditions which extremophiles require to survive were characteristic of our early EarthLikely that extremophiles evolved to dwell in such conditions billions of years ago and retained ability to survive today in specific environmentsHydrothermal vents?
13 Archaea differ from Bacteria in numerous ways Plasma membranes are made of different kinds of lipidsRNA and ribosomal proteins more like those of EukaryotesMostly anaerobic(photosynthetic: cyanobacteria and lithotrophs (Nitrosomonas which oxidizes ammonium)Photosynthetic
14 Domain Bacteria Two types: Refers to the Gram Stain (purple dye) Gram-positiveGram negativeRefers to the Gram Stain (purple dye)Gram-positive bacteria – possess a thicker peptidoglycan cell wall; retain stainGram-negative bacteria – contain less peptidoglycan; do not retain stain
16 Bacterial Conjugation Transfer of genetic materialHorizontal gene transferNOT sexually (no gametes)Involves cell to cell contact; does not involve fusion of gametes and the creation of a zygoteThere is not an equal exchange of genetic material, merely the transfer of genetic material from a donor cell to a recipientOften beneficial to the recipient cell – inc. antibiotic resistance or the ability to utilize a new metaboliteTransformation – genetic material transfer that does not involve cell to cell contact; direct uptake from environmentTranduction – incorporation of new DNA from virus
17 Eukaryotic originThe nucleus and endoplasmic reticulum arose from infolding of the prokaryotic cell membrane
18 Eukaryotic originEukaryotic organelles arose from a consortium of symbiotic prokaryotesMitochondria were aerobic heterotrophic prokaryotesChloroplasts (for photosynthesis) were photosynthetic prokaryotes
19 Endosymbiotic theory Evidence? Mitochondria have their own independent DNA, and a double membraneChloroplasts resemble cyanobacteria; also have their own independent DNA and a double membraneMitochondria generate ATP (powerhouse of cell); DNA analysis shows similarities to bacterial genomesChloroplasts originated as endosymbiotic cyanobacteria
21 Kingdom Protista (the trouble-maker) Kingdom Protista is NOT monophyleticThe 15 major protist phyla are now grouped into 7 monophyletic groups;There are 60 lineages that cannot be placed with any confidenceParaphyletic – includes common ancestor but not all descendents
22 Kingdom Protista Eukaryotic (must be! Domain Eukarya) Largely unicellular with some multi-cellular ‘exceptions’ (e.g., kelps, seaweed)May be autotrophic or heterotrophicDebate over classification –Are some protists members of other kingdoms?Would protists best be considered as several different kingdoms?
23 Kingdom Protista Characterized by: Mode of locomotion (e.g., flagella, cilia)Mode of nutrition (e.g., autotrophic, heterotrophic)Body form (unicellular, multicellular)Pigmentation (e.g., Red, Green, Brown alga)Reproduction (asexual, sexual)Essentially you are a protist if you are not clearly an animal, plant or fungus!Multicellular protists are distinguished from other Kingdoms by their lack of specialized tissues
28 Kingdom Fungi Unicellular and multi-cellular ~1.5 million species Important decomposersIncludes many disease-causing organismsOthers are important symbionts and fermenting organisms
29 Kingdom Fungi Mycology – the study of fungi All fungi are heterotrophicObtain their food by secreting digestive enzymes and absorbing the nutrients released by the enzymesUnicellular fungi may have flagella; multicellular fungi are primarily filamentous in formCell walls composed of chitinChitin: what crab shells are made of; a polysaccharide (carbohydrate)
30 Kingdom Fungi Six phyla Deuteromycetes – imperfect fungi – do not fit into the taxonomic classification; athletes foot, yeast infections, produce antibiotic PenicilinSexual form of reproduction never observed (only asexual known), sexual structures never seenSix phylaCytrids (flagellated), Zygomycetes (inc. bread molds), Glomeromycetes (mycorrhizae), Ascomycetes (inc. yeast), Bascidiomycetes (mushrooms), and Deuteromycetes (not pictured)
31 Kingdom FungiPhylogeny based on the 5 major Phyla (based on mode of sexual reproduction)
32 Kingdom FungiMulticellular fungi consist of long, slender filaments called hyphaeSome hyphae are continuous; others are divided by septaMycelium – a mass of connected hyphae
33 Kingdom Fungi Mycelium grows through and digests its substrate Fungi live in their food!
36 Kingdom Fungi Hyphae (mycelium) form complex structures A mushroom is a spore-bearing body of a fungus; composed of hyphaeA puffball is a spore-bearing body of certain species of fungi, including the deadly Death Cap mushroom; composed of hyphae
38 Kingdom Fungi Fungi can also be monokaryotic or dikaryotic Monokaryotic – one nucleus per cellDikaryotic – two nucleii per cellFungi reproduce sexually and asexuallyDuring sexual reproduction in some fungi, 2 haploid nuclei fuse creating a dikaryotic (dikaryon) stage, which precedes the normal diploid nucleus
39 Kingdom FungiSome fungi produce specialized mycelial structures to house spores (e.g., mushroom, puffballs, ‘shelf’ mcycelium on dead trees)Spores can form as a result of sexual or asexual reproductionSpores can withstand degradation and survive for long periods of time; because of their size, they can travel long distancesExplains worldwide presence of fungi, how disease spreads so easily
41 Kingdom FungiChestnut Blight – a fungal disease which has virtually eliminated the American chestnutAccidentally introduced into the U.S. on imported lumber from AsiaThe roots of the tree are fairly resistant to the fungus, but the tree succumbs once it grows enough shoots to reproduceUnknown spreading agent (the spores are everywhere!)
42 Kingdom Fungi1/4th of eastern American trees were Chestnuts, incredibly important for wildlife, only a few surviving – trying to breed resistant (Asian) chestnuts with American to save and restore; cankers caused by fungus cause limb to crack
43 …Jack Frost nippin’ at your nose… The American chestnut once covered large tracts of forest in the U.S.The chestnut was a very important source of food for wildlife (and the inspiration for at least 1 Christmas song…)At the turn of the twentieth century, one quarter of all trees in the eastern United States were chestnut!1/4th of eastern American trees were Chestnuts, incredibly important for wildlife, only a few surviving – trying to breed resistant (Asian) chestnuts with American to save and restore; cankers caused by fungus cause limb to crack
44 The Chestnut BlightOnly a few mature survivors remain of the American Chestnut, which once consisted of 4 billion trees (that’s over 99.99% gone)If you have ever eaten a chestnut, you had a European import; only our grandparents may have ever tasted an American chestnutThe American Chestnut Foundation seeks to restore the great chestnut, but how?
45 The Chestnut BlightDevelopment of blight-resistant American chestnuts is accomplished through a process known as “backcross breeding”Hybrids between American and Chinese chestnuts are repeatedly crossed back onto purely American specimens, yielding offspring which are blight- resistantThe resulting offspring are ~94% American (6% Chinese) and disease-resistant
46 Kingdom FungiSpores are frequently dispersed by wind, but may also be spread by insects and small animalsChytrids are an ancestral group and retain flagella; have motile zoospores
47 Why did the mushroom go to the party? Many fungi live underground, and can reach great sizesOne of the largest living organisms in the world is a fungus!The largest known specimen covers more than 3.4 square miles and is thousands of years oldAnd some species of fungi are bioluminescent!Believed to be 2400 years old
48 Connected underground by hyphae! Armillaria fungusConnected underground by hyphae!
49 Fungal EcologyFungi often have interactions or symbioses with other organismsObligate symbiosis – essential for survival; fungus cannot survive without symbiontFacultative symbiosis – fungus can survive without symbiontMutualistic relationships – both partners benefitCommensal relationships – one partner benefits, but the other is unaffected
50 Fungal EcologyA lichen is a symbiotic association between a fungus and a photosynthetic partner (usually green algae or cyanobacteria)Inhabit extreme environments – arctic tundra, hot deserts, rocky coasts, rainforests;widespread and long-lived, but subject to environmental disturbance (melanism!)
51 Fungal EcologyMycorrhizae – association between a fungus and the root of a treeMycorrhizae function as an extension of the plant root system; the fungus increases surface area for absorption and aids in transfer of nutrientsThe plant, in return, supplies organic carbon to the fungus92% of trees
52 Mycorrhizae Very important! Mycorrhizal plants are more resistant to drought and even microbrial soil-borne pathogensTwo typesArbuscular mycorrhizaeEctomycorrhizaeArb – penetrates the outer cells of the plant rootEcto – the hyphae surround but do NOT penetrate the cell walls of the roots
54 Fungal Ecology Leaf-cutter ants – an animal symbiont with fungi! The ants feed on special structures produced by a fungus that they have domesticatedThe ants feed the fungus leaves and protect it from pests and moldsIn return, the ants eat the fungus and feed it to their youngFungus grows only in the underground chambers of the ants nest
55 Just in case you didn’t believe me… I don’t think the smurfs are bioluminescent though!